Section 6. Marine Fecal Bacteria

Background

Fecal bacteria are found in the feces of humans and other homeothermic animals. They are monitored in recreational waters because they are good indicators of harmful pathogens that are more difficult to measure. The two types of fecal bacteria monitored in Puget Sound are fecal coliforms (including E. coli), which are gram-negative rod-shaped bacteria, and enterococci, which are gram-positive spherical bacteria. While fecal coliforms are more commonly monitored, enterococci are also measured because they have higher survival in salt water than coliforms and because they are thought to be more tightly associated with pathogens harmful to humans (Wymer et al. 2005). In Puget Sound, fecal pollution comes from both point-source origins such as combined sewer overflows and direct marine effluent discharge as well as non point-source origins such as surface water runoff, both of which increase with rainfall and river and stream discharge. In addition to serving as an indicator of pathogens, fecal bacterial pollution can also be an indicator of nutrient loading because sewage often contains high levels of nitrogen and phosphorous (Taslakian and Hardy 1976, Costanzo et al. 2001). Both point source (failing septic systems) and non-point sources (landscape features) contribute to fecal bacterial levels in Puget Sound. Additionally, shoreline and basin hydrology can affect the degree of retention of fecal coliform pollution such that bacteria may dissipate more slowly in enclosed bays with diminished water turnover. There currently are approximately 60 permitted wastewater treatment discharge locations in Puget Sound (Stark et al. 2009) (Figure 1) as well as numerous other storm drain and outfall locations.

In Puget Sound, monitoring of fecal bacteria is conducted by the Washington Department of Health, the Washington Department of Ecology and King County as part of the Puget Sound Ambient Monitoring Project (PSAMP) as well as other local municipalities. The Department of Ecology conducts monthly offshore surveys and assesses both fecal coliforms and enterococci at approximately 40 permanent stations along with a suite of locations that rotate each year (Janzen 1992, Newton et al. 2002)(Figure 2). The Department of Health (DOH) monitors fecal coliforms at 97 commercial shellfish growing areas in Puget Sound (Figure 3). The King County Department of Natural Resources and Parks monitors a combination of inshore and offshore targeted point-source (waste-water discharge) and ambient stations throughout central Puget Sound. The EPA-funded and jointly run (Departments of Health and Ecology) Beach Environmental Assessment, Communication and Health (BEACH) program monitors and reports on enterococci levels at marine swimming beaches throughout Puget Sound.

Figure 3. Commercial shellfish growing areas monitored by the Department of Health in 2007 with fecal pollution levels measured in Most Probable Number (MPN)/100m. Pie charts show the proportion of samples at each location with Good (≤ 30 MPN/100mL), Fair (>3 and ≤ 43 MPN/100mL) and Bad( > 43 MPN/100mL) fecal pollution levels (reprinted from Determan 2009; courtesy of Washington State Department of Health Shellfish Program).

Monitoring by all agencies is conducted with the intent of determining whether bacterial counts meet or exceed established critical levels. For fecal coliforms, the State of Washington (WAC 173-201, 1991) mandates that in class A and AA marine waters, bacterial counts should not exceed a geometric mean of 14 organisms/100mL with no more than 10 % exceeding 43 organisms/100mL (Newton et al. 2002). Similar standards for coliforms are mandated by the National Shellfish Sanitation Program (NSSP) for shellfish growing areas such that the geometric mean of an area cannot exceed 14 organisms/100mL or that the estimated 90th percentile cannot exceed 43 organisms for cases where only non-point sources are present. For enterococci, the minimum advisory standard recommended by the EPA for recreational beaches is 35 colonies/100mL (Schneider 2002, Wymer et al. 2005). Fecal coliform levels are also a component of Federal Clean Water Act standards. Two agencies, the Department of Health (Determan 2009) and King County (Stark et al. 2009), have developed indices to rank sites according to the frequency and intensity of increases above Washington State standards in observed fecal coliform levels.

Status and Trends

The most recently reported assessment of fecal coliforms by the Department of Ecology monitoring program revealed that the highest levels of coliforms were observed in Budd Inlet, Commencement Bay, Oakland Bay, Port Angeles Harbor, Possession Sound and Elliot Bay from 2001 – 2005 (Janzen 1992, methodology from Newton et al. 2002, reported in PSP 2007)(Figure 2). Of the 97 shellfish growing areas tested by the Department of Health in 2007, the highest fecal pollution levels were found in Filucy Bay, Drayton Harbor, Burley Lagoon and Port Susan (Determan 2009)(Figures 3, 4). Using a calculated Fecal Pollution Index, which integrates the frequency and intensity of events of elevated fecal coliform levels and ranges from 1 to 3, they found that the sound-wide FPI was 1.16 (Determan 2009). A trend analysis showed that the sound-wide FPI had not changed significantly from 1998 – 2007 (Determan 2009)(Figure 5). The Frequency of Exceedence (FOE) index of fecal coliform bacteria utilized by the King County shellfish area monitoring program identified Alki Point, Shilshole Bay, Fauntleroy Cove, Magnolia and Inner Elliott Bay as the locations with the highest FOE in 2004 (reported in PSP 2007, methodology from Stark et al. 2009)(Figure 1). The most recent enterococci levels reported by the BEACH program showed that of the 70 beaches monitored in 2004 and 2005, the highest number of exceedances were in locations that were largely on septic systems such as Birch Bay County Park and Bayview State Park, in enclosed bays such as Freeland Park as well as beaches in Sinclair and Dyes Inlets and Twanoh State Park (methodology from Schneider 2004, reported in PSP 2007)(Figure 7).

Figure 4. Department of Health rankings of 36 commercial shellfish growing areas in Puget Sound according to the fecal pollution index in 2007 (reprinted from Determan 2009; courtesy of Washington State Department of Health Shellfish Program).

Figure 6. Frequency Of Exceedence (FOE) index of fecal coliform bacteria from offshore and beach stations monitored by King County Department of Natural Resources and Parks in 2004 (reprinted from PSP 2007; methodology from Stark et al. 2009).

Figure 7. Monitoring sites for enterococci bacteria by the BEACH program (jointly run by the Department of Ecology and the Department of Health) and the number of times enterococci levels location exceeded program-defined guidelines (reprinted from PSP 2007; methodology from Schneider 2002, 2004).

Uncertainties

While fecal coliform levels in Puget Sound are well documented, disparate data sources make understanding broad spatial and temporal trends challenging, thereby obscuring potentially important patterns. Local hydrology, water temperature and salinity may all affect the persistence of fecal coliforms in Puget Sound yet this has not been investigated. Finally, the relative contribution of pet waste to overall fecal coliforms levels in Puget Sound has not been examined yet disease transfer from domestic pets to mammalian wildlife by this mechanism has been shown in other systems (Miller et al. 2002).

Summary

Considerable monitoring effort contributes to the assessment of fecal bacteria in Puget Sound. No single area or basin of Puget Sound was identified as consistently having the highest fecal coliform levels. A single analysis evaluating spatial and temporal trends based on all available data sources for fecal bacteria in Puget Sound has not been conducted.